The functions and functional regulation of microfilaments and microfilament activity are being explored during morphogenesis of embryonic mammalian salivary epithelium. The analogy between muscle action and microfilaments is being explored by low salt extraction and SDS polyacrylamide gel electrophoresis, polymerization-depolymerization properties, and heavy mesomyosin binding capabilities. Calcium ion requirement for filament activity and the possible presence and distribution of myosin are being tested. The relationship of morphogenesis to cytodifferentiation is being tested by abolishing morphogenesis and asking if cytodifferentiation can still take place. These experiments on the embryonic pancreas are designed to gain insight into the regulation of differentiation. Finally, the roles of collagen and mucopolysaccharides in embryonic lung and salivary gland morphogenesis are being investigated by analysis of the effects of specific inhibitors of the macromolecules on organ development in tissue culture.